The objectives of this project are to study in the experimental animal various aspects of thrombotic and nonthrombotic coronary occlusion, with particular emphasis on platelet behavior; their effects upon hemodynamic and electrical properties of the myocardium and the results of therapeutic intervention. Thrombotic, nonthrombotic and microcirculatory coronary occlusion will be induced and their characteristics and effects upon myocardium will be studied. In addition, the relationship of catecholamines to coronary microthrombosis will be explored. Therapeutic interventions, using antiplatelet aggregating agents, will be evaluated to obtain objective documentation (by means of parameters of cardiac function) of their postulated therapeutic value. A further objective is the in vivo diagnosis of coronary artery thrombosis. By means of a scintillation (Anger) camera and radioisotopically labeled agents participating in the formation or lysis of thrombus (fibrinogen, platelets, fibrinolytic agents) will attempt to obtain "images" of the underlying thrombus in various stages of its development. In addition, a biochemical approach (gel-chromatography) will be used to identify molecular changes of fibrinogen during and following experimental thrombosis. They will be directed at identifying, prospectively, patterns reflecting regional thrombotic events, to patterns obtained simultaneously from systemic blood at various time intervals following the thrombotic event.